The site glass is mounted on the Sump and gives a view into the sump to check the level of the hydraulic oil. It is recommended that the hydraulic oil level be maintained 1.2 way across the site glass. The oil level can drop (system use, torn AOS, frozen heat exchanger, etc.), or increase if water leaks into the oil (frozen heat exchanger, stuck check valve, etc.) Keeping it ½ way across the glass makes it easy to see changes. If the level is below the glass, how low is it? There is no way to tell if it is just below the glass or completely empty. The expensive compressor can only run a few seconds without hydraulic oil before it destroys itself by seizing up. Hydraulic oil is critical. If the oil level moves up above the glass line indicates the possibility of water mixing in with the oil. Diluted oil is also very bad for the compressor lubrication. A CAF operator can tell a lot and prevent big issues just by checking the site glass daily and periodically during CAF operations. Any changes should immediately be referred to you F-7 Certified EVT mechanic.
